Links of fitbit-derived sleep architecture and fragmentation with ADHD symptoms and externalizing behaviors in adolescents.

Sleep disturbances are linked to adolescent externalizing behaviors and attention-deficit/hyperactivity disorder (ADHD) symptoms. However, few studies have examined associations between objectively measured sleep architecture and these behavioral outcomes. This study investigated whether specific sleep stages and fragmentation are associated with externalizing behaviors and ADHD symptoms in a large U.S. population-based cohort. Participants were 4,545 adolescents (48.4% female; 73% White) from the Adolescent Brain Cognitive Development (ABCD) study with available Fitbit sleep data and parent-reported behavioral assessments. Sleep predictors included absolute duration and proportional time spent in rapid eye movement (REM), deep, and light sleep, as well as wake after sleep onset (WASO). Outcomes were externalizing behaviors and ADHD symptoms. Models adjusted for annual household income, sex, age, race, and weekend status. Lower REM sleep, both in absolute duration and relative proportion, was significantly associated with higher ADHD symptoms but not with externalizing behaviors after correction for multiple testing. Greater sleep fragmentation, indexed by longer absolute and relative WASO, was associated with elevated ADHD symptoms and, less robustly, externalizing behaviors. Light and deep sleep were not significantly associated with either outcome. REM sleep deficiency was associated with ADHD symptoms, whereas sleep fragmentation was associated with ADHD symptoms and, less robustly, with externalizing behaviors. Associations were cross-sectional; longitudinal and experimental studies are needed to determine whether these sleep characteristics contribute to, or could be targeted to improve, behavioral outcomes in adolescents.